 Exhaust cam timing.
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I finally tryed advancing my exhaust cam.It had been ruffly 20,000 miles since I reset the valves so while I was setting the valves I figured why not do it.I am happy to report I only had to reset one exhaust valve and no intakes.Anyhow I advanced the exhaust cam by one tooth.I am sorry to report I did not do a dyno run,lack of $$$$$. After setting it in there and checking my clearance again I turned it over by hand,engine felt ok and no bad noises.Then I assembled it somemore,and cranked it over with the wires off.Again it sounded good.So I started it up with the tank off,good.Put it all back together.Let her warm up.Sounds better,crisper,and throttle response seems a bit quicker.Took it around the yard at the shop.Sounds and feels much better!!  I rode it home and it is much more enjoyable to ride.My neighbor asked me if I had done something to the exhaust before I told him I had worked on it.He said it sounded much better.I think it is worth doing.One of my friends who rides a Yamaha heard it today and said it sounded better.I personally feel it has better throttle response and more grunt taking out.YES I am happy I took the time to do it.Sorry no dyno runs,maybe one day. 
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 Re: Exhaust cam timing.
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Joined: Jul 2007
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Worn Saddle
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Worn Saddle
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Hmmmm....very interesting. Any comments from the superior mechanics here? (I don't know enough to know if there are potential problems with this, but I'd be interested in learning.)
Fidelis et Fortis
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Re: Exhaust cam timing.
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Monkey Butt
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Monkey Butt
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Michael have you got the std engine etc or BB kit installed..
Ray(UK)
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Re: Exhaust cam timing.
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Joined: May 2007
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Worn Saddle
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Worn Saddle
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It should work pretty well as long as there's no physical collision...the valve overlap ought to provide superior combustion chamber scavenging and create better intake airflow characteristics. Of course, you'd have to couple that will a pretty free flowing exhaust system to get the most improvement.
You can't really know without a dyno run but I'll bet the one tooth advance would provide a slight broad range lift in the torque output.
A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. Herm Albright (1876 - 1944)
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Re: Exhaust cam timing.
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Joined: Sep 2006
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Learned Hand
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Learned Hand
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Surprised at your report. I tried the same thing last year after reading a couple of threads on the subject with dissapointing results. General consensus was this mod works best on 790, 360 degree engines.
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Re: Exhaust cam timing.
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My Speedmaster is a 2005 with the 865cc engine.I got the short TORs for mufflers,K&N factory replacement air filter,opened up air box and of course rejetted carbs.Riding it with the exhaust cam advanced one tooth since Saturday.Still happy with results.While I was doing it I did notice if you are not paying attention good while doing it, it would be easy to retard the cam one tooth instead of advancing it.This is do to it being drivin off the main timing gear in the center of the head that the timing chain actually drives.If somebody would actually retard the timing on the cam I could see it making it doggier all around,thus the opposit effect.Personally I am still happy I played around and tryed it.I got 38,500 miles on it now.I wish I would of done it long ago.
Last edited by Speedblue; 01/15/2008 2:33 AM.
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Re: Exhaust cam timing.
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Joined: Aug 2007
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Should be Riding
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Should be Riding
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does anyone know if this will positively affect a big bore motor with 790 cam?
Always remember to be yourself. Unless you suck. Then pretend to be someone else.
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Re: Exhaust cam timing.
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Joined: Jan 2005
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Old Hand
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Old Hand
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The 790 cams are really good as is. The 865 exhaust timing is more mild than a Model T Ford, which is why it responds well to just about any timing change. It is also the reason that other changes on the 865 are usually rather disappointing until you change the valve timing.
Let's hope there's intelligent life somewhere in space 'cause it's buggar all down here. -- Monte Python
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Re: Exhaust cam timing.
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When I looked at the cam while I had it out on my 865 I could not believe how simple and basic the cam lobes were.If dollars were abundant I would opt for aftermarket ones if any are worth the swap.I do know the cams are high dollar.
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Re: Exhaust cam timing.
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Joined: Jan 2005
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Old Hand
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Old Hand
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If you can find a 790 engine in a boneyard, you might be able to buy the exhaust cam out of it at a reasonable price. The 865 intake timing is not so bad, they just buggared up the exhaust to meet new emission requirements.
Let's hope there's intelligent life somewhere in space 'cause it's buggar all down here. -- Monte Python
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Re: Exhaust cam timing.
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Good idea Greybeard.Thanks.
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Re: Exhaust cam timing.
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Joined: Jul 2006
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Learned Hand
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Learned Hand
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Quote:
If you can find a 790 engine in a boneyard, you might be able to buy the exhaust cam out of it at a reasonable price. The 865 intake timing is not so bad, they just buggared up the exhaust to meet new emission requirements.
Wait! I thought the swap was a 790 exhaust cam into the 865 intake side  . (oddly enough, I'm being serious here)
2002 Bandit 1200/ GSXR cams/ 1277 BB Kit/ Holeshot header and can/ 38mm flatslides/ a good head/lotsa hp/lotsa tq- lots of rear tires...
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Re: Exhaust cam timing.
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Re: Exhaust cam timing.
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Should be Riding
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Should be Riding
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Blowing gravel off rural roads
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Re: Exhaust cam timing.
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Learned Hand
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I had to go back and look up a thread that Pat (Dinqua) responded to. His response was: Quote:
... you replace the [865] exhaust with an [790] intake cam...
There is a post on the "Cams" thread about someone that has done it and his gains.
...but I couldn't find the post in cams
2002 Bandit 1200/ GSXR cams/ 1277 BB Kit/ Holeshot header and can/ 38mm flatslides/ a good head/lotsa hp/lotsa tq- lots of rear tires...
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Re: Exhaust cam timing.
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What about the 790 engine? Would advancing the exhaust cam a tooth have a similar effect on the 790 engine?
Its more fun to be ridin'! I'm still ridin 
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Re: Exhaust cam timing.
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Joined: Sep 2006
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Learned Hand
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Learned Hand
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Quote:
What about the 790 engine? Would advancing the exhaust cam a tooth have a similar effect on the 790 engine?
I tried it. Performance suffered. Changed it back. Lengthy thread on Delphi forum. Works on 790cc, 360 degree engines like standard Bonnevilles, not 270 degree America engines.
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Re: Exhaust cam timing.
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I did this on mine for a while, The exhaust sounded cooler the torque was up a bit it seemed..Top end I felt sufffered a bit, and in the end I just changed it back.
"Got the wind in my face the road goes on for miles...."
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Re: Exhaust cam timing.
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i have played around with the intake and exhaust cams a bit, just from a seat of the pants dyno i like the exhaust left stock and advanced the intake cam 1 tooth.
2004 america 790 cc/270* crank.
GRAND MASTER WIZARD
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Re: Exhaust cam timing.
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i can't find it either.....anyone have a good link handy...i'm thinking of changing the exhaust cam this year as well.
not going to bother if it isn't a decent difference.
edit=I was refering to the 'cams' thread mentioned...I tried to quote another post but i guess it didn't go through.....LOL
anyway, if I could find some numbers on before and after dyno's I might be interested in hunting down an exhaust cam.
Last edited by Tony_From_Boston; 03/05/2008 5:02 PM.
-Tony
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